Near-infrared sensors are used in the medical industry to measure the amount of oxygen saturation in a patient's blood or tissue. These sensors work by detecting light after it has traveled through a portion of the patient's body. However, ambient or other light may interfere with the sensor, providing medical personnel with false readings that may lead to missed diagnoses and incorrect treatments. Existing solutions to blocking ambient light results in sensors that are bulky and expensive to manufacture. Moreover, these bulky sensors are not very flexible and cannot always conform to the contours of a patient's body. Accordingly, a physiological sensor is needed that protects against interference from ambient and other forms of light but is flexible enough to conform to the contours of the patient's body.